Technical Field
This Patent Disclosure relates generally to resonant inductive sensors and sensing, such as can be used in sensing position, proximity or physical state or condition.
Related Art
A resonant sensor includes a resonator configured for operation in a resonance state (resonant frequency and amplitude). Sensor electronics drives the resonator with an AC excitation current synchronized with resonator oscillation voltage to maintain resonance (sustained, steady-state oscillation), overcoming a resonator loss factor represented by a resonator impedance (such as series/parallel resistance Rs/Rp). For example, in the case of inductive sensing, the resonator includes an inductive sensing coil that operated at resonance projects a magnetic sensing field.
Resonant sensing is based on changes in resonance state manifested by, for example, changes in resonator oscillation amplitude and frequency resulting from changes in resonator impedance in response to a conductive target. For example, in case of inductive sensing, resonance is affected by a storage or loss in projected magnetic flux energy output from the inductive sensing coil, such as caused by the eddy current effect associated with a conductive target. This sensor response is manifested as a change in resonator impedance (loss factor Rs/Rp).